Patent GB-1511722-A (GB)
Title: Device for changing the gears automatically on a synchronised gearbox
IPC: F16H61/02
Filed: 1975-03-25
Abstract: 1511722 Change-Speed control AUTOMOBILES M BERLIET 25 March 1975 [29 March 1974] 12456/75 Heading F2D A system for controlling manual or automatic ratio shifts in a motor vehicle transmission having a main clutch and a gear-box with internal or external synchronizing means includes a comparator 302 for comparing a signal from an electronic logic circuit 200 indicating a desired ratio with a signal from a device 500 detecting the existing ratio, the signals being received by the comparator without storage in memory devices, except during a shift. The shift circuit has stores, memories, and code parity checks which must be satisfied at each stage of a shift sequence for the shift order to proceed. The circuit distinguishes between upshift and downshift, and receives an input at 323a from an external synchronizer, where provided. A delay device 308 is effective following an upshift to ensure time for the vehicle speed to increase before another shift is initiated. The main clutch is released during shift. The signal from the ratio selector 200 passes through a temporary code store 301 to the comparator 302, where it is compared with the established ratio detected at 500. If the selected and established ratios are the same, the comparator 302 issues no signal, but, if different, it issues a zero shift signal to a delay circuit 303, and one of two additional signals 302a, 302b indicating upshift or downshift to the shiftdirection store 326. At this stage neither store 301, 326 has received an order to store its signal. The delay circuit 303 prevents undesired transient shifts, and the zero shift signal therefrom is inverted to a "1" in a NOT circuit 304 and passed to an AND gate 305 which issues the command signal for the shift to proceed, but before this command can issue the AND gate 305 must be unlocked by two additional input signals, one from a detector circuit 306 which checks the validity of the selected ratio codes received, the other from an AND gate 331 opened by signals from parity checks 329, 330 of the shift and selector controls 400, 200. The shift command signal from the AND gate 305 issues four commands, a first to release the main clutch at 305a, a second an order to store to the shift-direction store 326, a third, through a time delay 308, to an AND gate 309, which, when opened as described below, issues an order to store to the selected ratio code store 301, and a fourth to a neutralizing and shift circuit which is as follows. Neutralizing.-At the commencement of a shift, with a ratio established in the transmission, the transmission condition detector 500 signals a neutral decoder 316 to issue a zero signal to a neutral memory 317, which issues a zero to a NOT gate 318. The neutral memory 317 receives an order to store from the shift command gate 305 through an AND gate 315, which is opened by a "1" from a NOT circuit 328 when a "0" is issued to the latter by an "AND" gate 327, opened by two signals, one from the AND gate 331 released by the parity checks 329, 330, the other, through a time delay 312, from a second binary comparator 311, which compares the codes of ratio selected 200 and ratio stored 301. Neutral is now established at the control 400 by the shift command signal from 305 passing through an OR gate 314, AND gates 319, 321, the latter opened by a neutral code generator 320, and OR gate 322. Ratio establishing.-With neutral now established, the ratio condition detector 500, through the neutral coder 316, changes the output signal of the neutral memory 317 from "0" to "1", which locks the gates 319, 321, preventing any further neutralizing action during the shift, and the "1" at 317 opens AND gates 323, 324, permitting the imposed ratio signal from the store 301 to pass through the OR gate 322 and establish at 400 the ratio selected at 200. This action causes the ratio detector 500 to erase the signals to the neutral coder and memory 316, 317, and restore parity in the comparator 302, which erases the shift command signal from 305, permitting the main clutch to re-engage, subject to two time delays 325, the first 325a sufficient for normal shift duration, the additional second time 325b to allow extra time for a pulsed re-engagement if the selector dog clutch teeth abut end on, and also, through the AND gate 309 cancelling the order to store on 301, after a time delay 308, effective after upshift only, being inhibited for downshift. Release of the AND gate 323, which passes the shift signal, is subject to an "external condition" signal, which may be in response to completion of synchronization of the new ratio by external means. Absence of agreement on the parity checks 329, 330 during shift activates an alarm through a NOT circuit 332. If, during the progress of a shift, a new ratio is signalled by the selector 200, this will produce a signal from the comparator 311, which, through delay 312, and gates 327, 328 and 315 will delete the neutral memory 317, but, in this case, neutral will still be held through 311, 312, 327, 314, 319, 320, 321, 322 and 400.